Radio Control Info Articles

Torque vs Horsepower

In this article we are going to look at Torque vs Horsepower and settle that debate once and for all. We will be focusing in on how these terms work for us in the RC hobby.

Many questions that you may see pop up or often question yourself in the world of RC are the following:

What is Power?
What is Torque?
Does Torque or Horsepower win RC races?
Does Horsepower sell engines?
Do Electric Motors produce more power or torque vs gas or nitro engines?

We will be answering these questions throughout.

What is Power? – Torque vs Horsepower

Power is simply defined as the amount of work that can be performed at a specific rate. This just means that if you have power, you can perform work that accomplishes tasks. Generally we are talking about mechanical power when looking at torque vs horsepower. The important factor to remember in the definition of Power is that mechanical power is the product of Torque and RPM, where RPM is revolutions per minute.When we talk about mechanical power we are considering torque already but at a certain RPM. The unit of power is horsepower, watts, kilowatts. etc. Nitro or Gas engines use horsepower where Electric motors use watts or kilowatts. 746 watts is equivalent to 1 horsepower. Before we look at what torque is I will leave you with the formula to calculate Horsepower. P = T ω. Now we will define and better understand what torque is.

What is Torque? – Torque vs Horsepower

Torque production – Torque vs Horsepower

Torque is best defined or explained by looking at static torque. When we take a Torque Wrench and apply an appropriate amount of force on the handle of the wrench we create a torque at the socket. The force applied at a distance produces a torque that can be used to tighten bolts such as lug nuts found on your car. This torque is static meaning you can not perform any work when peak torque is reached as nothing will move.

Now if we consider dynamic torque, the exact same action is happening except the torque is being applied constantly as a shaft rotates continuously.

In conclusion, torque creates a twisting or turning force to a shaft or flywheel. Torque can be measure in inch-ounces, pound-feet, or Newton-meters.

If we consider the torque vs horsepower characteristics of an electric motor verse a nitro or gas engine, they are fairly different. The power/torque curve of an internal combustion engine such as the nitro or gas engine is quite linear, where power builds as RPM increases and torque increases as RPM increases. Eventually torque levels off and begins to decline.

Now when we consider the electric motor, the characteristics are quite different. Torque is exceptionally strong in the lower RPM ranges and then tapers off at the higher RPM range. Horsepower build strongly at the lower RPM range as the amount of torque available is significant. Using the graph to the side, you can visually see the difference between the two power sources mainly in the torque curves.

The nitro and gas engines tend to perform very well at the higher RPM range and the electric motor tends to perform very well at the lower RPM range. The most important characteristic to take from this is the torque curve and how it forms for each power source. Although these characteristics are very evident in general terms, it is important to remember that these curves can vary dependent on specific motor or engine characteristics.

Does Horsepower sell engines? – Torque vs Horsepower

The real answer to this question is not necessarily as technical as much as it is a marketing explanation. When you are looking at power values of combustion engines specifically, you must take this information with a grain of salt. It is easy to publish values in order to make a product appear more superior against the competition.

Now if we change the question so that it reads Does true Horsepower values sell engines? If we can be assured that the horsepower value of a specific engine is accurate, the answer to the question should be – it should definitely help. We will investigate the answer a little further in the next question below.

This question is rather interesting and often pops up in many forums around the internet, focusing in on which characteristic provides the solution to racing.

Now if you already have read up to this point in the article, you have 85 percent of the answer to this question. This is why:

If we look at the definition of torque, torque is its own entity. When looking at horsepower, power in itself is not its own entity. The interesting part of horsepower is that the equation for it includes torque, where Power equals torque multiplied by RPM! This is very relevant as when we are talking about power, we are really just talking about torque but at a specific RPM.

Consider this question: A car outputs 1 horsepower and 1 pound feet of torque somewhere in its power band at the engine. If we assume no power train losses and look at a transmission with a ratio of 1:1, what is the torque and power after the transmission.

Well this question may appear easy, the correct answer would be, after the transmission we would see 1 horsepower and 1 foot pounds of torque.

Let’s add a twist to the question. What if we use the exact same scenario but with a transmission that has a 1:2 ratio? That is where the output shaft turns once and the engine turns two revolutions.

The correct answer is that the horsepower remains at 1 and the torque at the output shaft from the transmission doubles to 2 pound feet .

We actually gain torque by sacrificing RPM. Remember Horsepower is derived from torque and RPM. Why would we want to purchase an engine based on torque values vs horsepower values when we can manipulate the torque values ourselves and we can NOT change the horsepower values.

What would you Choose? – Torque vs Horsepower

Would you choose Engine One or Engine Two?

Engine One has 0.5 horsepower and 1 pound feet of torque

Engine Two has 1 horsepower and 0.5 pound feet of torque.

If it was up to me and I wanted to win races, I would most definitely select the engine that has the higher horsepower. I know that if I require more torque at a certain speed I can just manipulate the gear ratio in my transmission to provide me with a better torque value. However if I selected the engine with a lower horsepower, I can not alter the horsepower value to improve it. Regardless of what transmission is used, the power output never changes.

Therefore engine Two has the most potential to win races.

Conclusion – Torque vs Horsepower

Horsepower wins races, torque just confuses people with what is actually occurring. Horsepower is derived from torque and RPM, when you are talking about horsepower you are talking about torque at a specific RPM. Horsepower accomplishes work, the more of it you have, the more you can do. That is purely by definition.

Nitro and Gas engines have great power curves but the torque curve of an electric motor provides it a large advantage. A stronger torque curve means an electric motor has a lot of horsepower available at low RPM’s. Having a lot of horsepower at low RPM’s is a great way to get a heavy RC vehicle off the starting line.